Mark IIB to IIC+ Conversion
- Thread starter Jay Omega
- Start date
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Looks good! 👍
Board is mostly populated now, I’ll start adding wires and a few components and get the install going.
I’d ordered some VTL5C4s off the net, I thought they were NOS but after closer inspection they look like imposters. Hopefully they run OK, the forward voltage was a bit higher than the VTL5C1s, so worst case I’ll have a touch higher Q in the EQ. I don’t care much about the lead master min setting loudness. Maybe I’ll try an alternative, I plan to test them out before I install the card to see if I’m happy enough
Tested the switching last night, unfortunately got 13k on resistance for the lead master VTL5C4. Back to the drawing board, don’t know if I’ll try to source some originals or modify the circuit yet
Don't understand. You're building it exactly to specs. Bad Vactrol?
They've long since stopped making the vactrols that Boogie used. The VTL5C4 replacements I have don't act the same in the circuit
Alrighty, in case anyone else runs into this issue with sourcing VTL5C4s, I tested Advanced Photonix NSL-32SR2 in the stock circuit and the lead master LDR on resistance was around 500 ohms, and the EQ LDR on resistance was around 50 ohms. @Henz was kind enough to do some testing in his DRG, his lead master LDR was around 250 ohms, and EQ LDR was around 125 ohms when they were on.
I've replaced the lead master LDR with the NSL-32SR2 as I'm happy with 500 ohms. I also bought two, what appear to be, NOS Vactec VTL5C4s and they should be here on Thursday. Will test that in the EQ, if it doesn't work out I'd be happy with the NSL-32SR2 there, should give a touch higher Q factor to the EQ. In the Mark V they basically shunt straight to ground, so Boogie didn't think having some resistance there was super important
I've replaced the lead master LDR with the NSL-32SR2 as I'm happy with 500 ohms. I also bought two, what appear to be, NOS Vactec VTL5C4s and they should be here on Thursday. Will test that in the EQ, if it doesn't work out I'd be happy with the NSL-32SR2 there, should give a touch higher Q factor to the EQ. In the Mark V they basically shunt straight to ground, so Boogie didn't think having some resistance there was super important
Great work
Amazing! 👍
She’s alive and she’s a gnarly beast!!
Not finished but good enough to rock for a couple days now. Not sure if my pot tapers are the same as Boogie’s, thinking I might setup the Mark IV how I like and measure to compare when I get some time.
A few more things to test, but feeling pretty confident with the preamp board design. I plan to change a few things and do a prototype run of three boards from a board house in the future.
Not finished but good enough to rock for a couple days now. Not sure if my pot tapers are the same as Boogie’s, thinking I might setup the Mark IV how I like and measure to compare when I get some time.
A few more things to test, but feeling pretty confident with the preamp board design. I plan to change a few things and do a prototype run of three boards from a board house in the future.
electric mayhem
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That's f'ing awesome!
Hahah thanks! The thing rips, it's crazy loud. Can't wait to get this IIB converted
I’d probably sell ones made by a board house, not the hand made jobbies. When I convert the IIB it will be a board from a MFG, this project was a proof of concept. I didn’t think there would be much interest in these, but I could get as few as three made at a time.
I did find an issue with the amp yesterday when testing the effects loop. I have a few things to figure out yet
I did find an issue with the amp yesterday when testing the effects loop. I have a few things to figure out yet
Turns out the “issue” I found with the effects loop seems to be normal, I checked my Mark III and it does the same thing.
There is a small amount of hum / buzz, which I’m hypersensitive to, but when I fire up my Mark III the fan drowns it out, so I don’t think it’s any different from a normal Boogie.
Maybe it’s time to stick the fork in and call this good! I cranked it up today and was able to get really good sounds out of it, I think the only pot tapers that are off are the master volume because I had to use a 250k instead of 100k, and my lead master as I have 4-5x the LDR ground resistance compared to the real deal.
There is a small amount of hum / buzz, which I’m hypersensitive to, but when I fire up my Mark III the fan drowns it out, so I don’t think it’s any different from a normal Boogie.
Maybe it’s time to stick the fork in and call this good! I cranked it up today and was able to get really good sounds out of it, I think the only pot tapers that are off are the master volume because I had to use a 250k instead of 100k, and my lead master as I have 4-5x the LDR ground resistance compared to the real deal.
